What is the best "soft" way to speed up my computer?

I use a PC with XP at work with P4 3 GHz CPU and 2GB RAM. It seems like this would be sufficient to run Office and the other work applications, but I find myself sitting and loading all the time. I have even tried cleaning up the drive with the following apps:
– Spybot Search & Destroy
– Revo Uninstaller
– Antivirus Guard Free
– CCleaner
– Auslogics Disk Defrag

I can’t think of anything else to do to speed this baby up using software. Is my next option just hardware-related?